An electrical load which receives power through an AC power system is generally designed to operate reliably when the actual supply input voltage is within approximately 10% of the rated supply input voltage. A voltage sag (or dip) can refer to a temporary reduction of the rms AC voltage in which the actual supply input voltage is below approximately 90% of the rated supply input voltage, for example. Voltage sags can be caused by various reasons, such as startup of a large load within a facility, a circuit fault, a fault on the utility transmission or distribution system, a problem with a generator, or any of a number of other reasons. Voltage sags can cause difficulties in industrial manufacturing facilities or other facilities with heavy machinery. For example, voltage sags can cause equipment to shut down and/or be damaged. Such instances can be costly due to down time, repair, and/or replacement of machinery due to voltage sags. Accordingly, voltage-sag testing can be used to determine the voltage tolerance of certain equipment.